In a fiber optic link, optical signals are transmitted via an optical fiber from a transmitter which comprises a light emitting device such as an LED or diode laser to a receiver which comprises a detector such as a PIN diode. The determination of coupled optical power as a function of position is important in the engineering of the LED-to-fiber coupling in the transmitter and the fiber-to-PIN diode coupling in the receiver
In particular, when a fiber optic link is designed, it is desirable to achieve maximum LED-to-fiber and fiber-to-PIN diode coupling. Thus, a fiber link is preferably designed with a good understanding of how the coupling varies with variations of the fiber position relative to the position of peak LED output intensity in the case of the transmitter or the position of peak PIN diode detection sensitivity in the case of the receiver. In other words, it is important to know the tolerances of the LED-to-fiber coupling in the transmitter and the fiber-to-PIN diode coupling in the receiver.
To determine such tolerances, it is necessary to determine the optical output intensity of the LEDs as a function of position relative to the maximum output intensity. Similarly, in the case of a PIN diode, it is necessary to determine the detection sensitivity of a pin diode as a function of position relative to the peak detection sensitivity.
This information provides significant benefits. For example, a very expensive transmitter due to tight LED-to-fiber tolerancing would not be necessary if the output intensity of the LED does not decrease significantly as the position of the fiber is offset from the position of peak output intensity. On the other hand, tight tolerances would be important if the output intensity of an LED varied sharply relative to the position of peak output intensity. In short, in order to design an optimal optical fiber link, it is desirable to understand how the power coupled between an optical-electronic device and an optical fiber degrades with varying offset.
In view of the above, it is an object of the present invention to provide a method and an apparatus which enables the characterization of optical-electronic devices such as LEDs and PIN diodes for coupled power degradation with varying offset.
It is a further object of the invention to provide a method and an apparatus which enables the determination of output intensity profiles for LEDs and other light emitting devices.
It is also an object of the invention to provide a method and an apparatus which enables the determination of detection sensitivity profiles for PIN diodes and other light detecting devices.